Six male volunteers for dry Immersion (DI) modeling the microgravity effects on human organism were subjects In the GI evacuatory function investigation. The investigation was aimed to evaluate liquid food evacuation from the stomach (13C-acetate test) and time of chymus orocecal transit (H2-inulin test). The 13C-acetate test did not reveal changes in stomach evacuatory activity after 4 days in DI. The H 2-Inulin test demonstrated shortening of chymus transit along the small intestine and extension of chymus passage from the ileum to cecum. Subsequent reduction of inulin metabolism in the large intestine suggested inhibited passage of these GI segments. The results showed that stability of liquid evacuation from the stomach and acceleration of chymus transit along the small intestine hinder evacuation of the large Intestine content which is the primary cause for Inhibition of GI evacuatory activity In DI.